Method of manufacture of polishing pads having two or more endpoint detection windows

ABSTRACT

A chemical mechanical polishing pad having two or more end point detection windows can be made by providing a structure that includes a polishing layer having a top surface defining a horizontal direction, a bottom surface, and two or more apertures extending from the top surface to the bottom surface wherein each of the two or more apertures has a transparent window located in the aperture, wherein each of the windows has a portion extending outward from the bottom surface of the polishing layer, wherein the two or more apertures are located at select distance from each other, applying a subpad material on the bottom surface and the portion of the windows extending outward from the bottom surface, and revealing the windows by removing a portion of the subpad material and wherein the two or more apertures remain at the select distance from each other.

FIELD OF THE INVENTION

The field of this invention is a method of making polishing pads havingmore than one endpoint detection windows.

BACKGROUND

Chemical Mechanical Planarization (CMP) is a variation of a polishingprocess that is widely used to flatten, or planarize, the layers ofconstruction of an integrated circuit or similar structure. The processis often used as part of the manufacture when using lithography withmultiple deposition steps, in order to precisely build multilayerthree-dimensional structure or circuitry. The layer to be polished istypically a thin film (e.g. less than 10,000 Angstroms) that has beendeposited on an underlying substrate. The objectives of CMP are toremove excess material on the substrate (e.g. wafer) surface to producean extremely flat layer of a uniform thickness, the uniformity extendingacross the entire substrate (e.g. wafer) area.

CMP utilizes a liquid, often called slurry, which can contain nano-sizedparticles. The slurry is fed onto the surface of a rotating multilayerpolymer pad (sometimes referred to as polishing sheet), the pad beingmounted on a rotating platen. Substrates (e.g. wafers) are mounted intoa separate fixture, or carrier, which has a separate means of rotation,and pressed against the surface of the pad under a controlled load. Thiscan lead to a high rate of relative motion between the substrate (e.g.wafer) and the polishing pad and a resulting high rate of shear orabrasion at both the substrate and the pad surface. The shear incombination with the slurry particles trapped at the pad/substratejunction abrade the substrate (e.g. wafer) surface, leading to removalof material from the substrate surface. Control of removal rate and theuniformity of removal are important.

Commercial CMP pads are multilayer composites. In addition to an upperpolishing layer, which contacts the substrate (e.g. wafer) to bepolished, one or more subpad layers are employed to adjust thecompliance of the pad under pressure, particularly over the full area ofthe pad, to better achieve the required film uniformity across the fullsubstrate (e.g. wafer) surface. Controlled increase in compliance can beachieve by using a subpad material of lower modulus than the upper layerand adjusting the relative thicknesses of both layers to achieve thedesired result.

In order to precisely control the final thickness of the polished film(the endpoint), film measurement during polishing is widely employed.There are two main metrology approaches for endpointing. One approachfor endpoint detection uses transmittance of desired wavelengths oflight through the polishing pad, the light reflects from the substratebeing polished, and the reflected light signal then passes back to theinterferometer, which processes the reflectance signal to determine ifthe polishing has reached its desired goal (e.g., film thickness,intended reveal of an underlying structure). The metrology equipment canbe located within the body of the platen that holds the pad. In someinstances, the optical equipment may extend above the platen into theplane of the subpad layers of the CMP pad. Thus, a recess may be desiredin the subpad where the window is placed.

This method requires the polishing pad to have at least a portion to betransparent to the wavelengths of light being used in theinterferometer. In some pad designs this is achieved by providing awindow material of a different composition than the upper pad layer isdisposed in an aperture within the pad since many polishing layermaterials are opaque. Use of such windows requires alignment ofapertures in both the polishing layer and the subpad layer(s).

As integrated circuit dimensions scale down, increasingly accuratereal-time film thickness measurements are critical for process control.This has led to the adoption of multiple endpoint units per platen andthe use of multispectral optics to allow accurate real-time measurementsof film thickness profiles via triangulation and signal processing.Further, to avoid reducing the area for polishing, it can be desirableto reduce the aperture size (window size). As a result, themanufacturing tolerances of current CMP pad windows are becoming morestringent. In addition, maintaining alignment of windows with respect topolishing layer and subpad layer apertures can be challenging. Forinstance, when forming the multi-layer pad (e.g. by lamination or thelike) the differing materials of the polishing and subpad layers mayshrink or stretch in different proportions causing misalignment suchthat the aperture in the subpad does not align with the window or doesnot align with the aperture in the polishing layer. Also, in formingseparate apertures in each layer and then laminating, the pre-formedapertures may not have been in completely consistent locations to enablefull alignment of more than two apertures or the aperture and windows inthe layers. For example, if there are two apertures in each of thepolishing layer and the subpad layer(s) if those are formed at aslightly distinct distance in each layer, then it will be impossible tohave full alignment. Total misalignment—e.g., where there is no overlapof the apertures of the subpad and polishing layer or no overlap of thewindow with one of the apertures—would prevent any use of the window.Partial misalignment—e.g., where the subpad aperture overlaps partiallywith the window—can narrow the transparent region enough to make itdifficult to use for end detection (for example by producing attenuationand noise during measurements that can lead to endpoint detectionerrors). The misalignment issues can be particularly problematic in padswith multiple windows with smaller aperture sizes. Accordingly, a padmanufacturing process capable of producing a multilayer window pad in asimplified manufacturing process with increased window locationprecision in all dimensions that is useful for a wide variety of top padmaterials would represent a significant improvement in the art.

SUMMARY OF THE INVENTION

Disclosed herein is a method of manufacturing a chemical mechanicalpolishing pad having two or more end point detection windows comprisingproviding a structure that includes a polishing layer having a topsurface defining a horizontal direction, a bottom surface, and two ormore apertures extending from the top surface to the bottom surfacewherein each of the two or more apertures has a transparent windowlocated in the aperture, wherein each of the windows has a portionextending outward from the bottom surface of the polishing layer,wherein the two or more apertures are located at select distance fromeach other, applying a subpad material on the bottom surface of thepolishing layer and wherein the two or more apertures remain at theselect distance from each other and the portion of the windows extendingoutward from the bottom surface, and revealing the windows by removing aportion of the subpad material.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the figures, which are exemplary embodiments, andwherein the like elements are numbered alike.

FIG. 1a is a top view of a pad having three windows.

FIG. 1b is a cross-section view of a portion of the pad of FIG. 1.a.showing the layers of the pad and one window.

FIG. 2 is a schematic view of a window.

FIG. 3 is a side view of a window.

FIG. 4a-4i represent a sequential series of cross section views thatillustrate forming a pad and subpad with multiple windows in accordancewith the method of the invention.

FIG. 5 is a cross section of a portion of a pad having a window as inFIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

The present application is a method of forming a pad that allows forprecise locating of more than one window in the pad. The method avoidsthe problems of misalignment of apertures in the subpad with theapertures in the polishing layer and misalignment of the windows in theapertures. Such misalignment may be caused for example by one or more ofthe following: by different coefficients of thermal expansion in thelayers, different stretching of deformation of the layers duringmanufacture, imprecise location of apertures in two different layers,imprecise alignment of apertures during lamination, or the like, or acombination of two or more of those causes.

Thus, the method comprises providing a polishing layer having a topsurface defining a horizontal direction, a bottom surface (also referredto herein as an interface surface), and two or more apertures extendingfrom the top surface to the bottom surface, wherein each of the two ormore apertures is located at a select distance from the otheraperture(s). Located in the aperture, is a transparent window. Thewindows each include a portion extending outward from the bottom surfaceof the polishing layer. The method includes applying a subpad materialon the bottom surface and the portion of the windows extending outwardfrom the bottom surface, and then removing a portion of the subpadmaterial to expose the windows. This method ensures alignment of thewindows with the apertures in the polishing layer as each window islocated in one of such apertures. This method further ensures alignmentof the polishing layer aperture windows with the aperture in the subpad.

FIG. 1a is a top view of one example of a pad made by the methoddisclosed herein. The pad 01 has a top surface 03. Although not shown,the top surface 03 can have a surface roughness or a surface patternsuch as grooves or perforations. This pad has three windows 04 locatedat select distances, d_(s1), d_(s2), and d_(s3), from each other. Theselect distances can be the same or different. As examples of windowplacement and orientation: each window could be placed at the sameradial distance from the center 07 of the pad or each window could beplaced at a different distance from the center 07 of the pad; thewindows could be equidistant from each other or the windows can benon-equidistant from each other. Most advantageously all windows are atthe same radial distance from the center 07. The select distance(s) canbe selected to correspond to the placement of endpoint detection sensorsin a tool or platen for chemical mechanical polishing. Each window 04can be the same size. Each window 04 can be of the same shape. Eachwindow 04 can be of the same material. Alternatively, a first window canbe of a different size, a different shape, or a different material froma second window or any third or more windows. At least two of thewindows are transparent to the wavelength of radiation (e.g. light) usedin the sensor. The windows can be made from a polymer or polymer blendsdesired so long as it has sufficient transmission at the wavelengthsused by the optical metrology. It can be helpful if that window materialhas a hardness and thermal expansion coefficient similar to that of thematerial used in the polishing layer. Examples of window materialsinclude polyurethanes, acrylic polymers, cyclic olefin co-polymers (e.g.TOPAS 8007, etc.). Use of polyurethane materials can be helpful in padswhere the polishing layer and subpad layer(s) are also polyurethanes.Advantageously, the window has transmission to as low of wavelength aspossible, such as that achieve with windows manufactured with aliphaticpolyurethanes or other materials having optical transparency.

FIG. 1b shows a cross-section of a portion of a pad. The pad includes apolishing layer 05 and a subpad 06. The window 04 shown in FIG. 1b has aplug shape. The polishing layer 05 can comprise a polymeric material. Itcan optionally include pores and or particulates. Pores can be provided,for example, by addition of hollow flexible polymer elements (e.g.hollow microspheres), blowing agents, frothing or supercritical carbondioxide. Examples of polymeric materials for the polishing layer includepolyurethanes, polycarbonates, polysulfones, nylons, polyethers,polyesters, polystyrenes, acrylic polymers, polymethyl methacrylates,polyvinylchlorides, polyvinyl fluorides, polyethylenes, polypropylenes,polybutadienes, polyethylene imines, polyether sulfones, polyamides,polyether imides, polyketones, epoxy resins, silicones, copolymersthereof (such as, polyether-polyester copolymers), and combinations orblends thereof. The polishing layer 05 can comprise a polymer that is apolyurethane formed by reaction of one or more polyfunctionalisocyanates and one or more polyols.

The subpad layer 06 can comprise one or more layers. The subpad layer(s)can comprise a material that is more compliant than the material of thepolishing layer 05. The subpad layer(s) 06 can comprise a polymericmaterial. The subpad 06 can comprise a porous layer. Examples ofpolymeric materials for the subpad layer(s) include polyurethanes,polycarbonates, polysulfones, nylons, epoxy resins, polyethers,polyesters, polystyrenes, acrylic polymers, polymethyl methacrylates,polyvinylchlorides, polyvinyl fluorides, polyethylenes, polypropylenes,polybutadienes, polyethylene imines, polyether sulfones, polyamides,polyether imides, polyketones, silicones, copolymers thereof (such as,polyether-polyester copolymers), and combinations or blends thereof.

FIGS. 2 and 3 show other window shapes. The window 204 in FIG. 2 has anupper portion 204 u and a lower portion 204 l, each portion beingcylindrical or oval. The upper portion 204 u has a dimension (e.g.diameter) d_(u) that is smaller than the dimension (e.g. diameter),d_(l), of the lower portion 204 l such that a rim 204 r is formed. Thelower portion can form a flange portion. In FIG. 3 a cross section of asimilar window 304 is shown that include an upper portion 304 u, amiddle portion 304 m, and a lower portion 304 l. The middle portion 304m has a dimension (e.g. a diameter) in the horizontal direction that islarger than the dimension of either the upper portion 304 u or the lowerportion 304 l, thus forming an upper rim 304 ur and a lower rim 3041 r.The middle portion can form a flange portion. While FIG. 3 shows thelower portion 304 l having a dimension in the horizontal direction thatis smaller than the dimension in the horizontal direction of the upperportion 304 u, those dimensions could in the alternative beapproximately the same size. Generally the window dimensions in thehorizontal direction are on the order of 8 to 18 mm. Generally theoverall height of the window is less than the overall thickness of thepad. For example, the overall height (e.g. h_(total)) of the window canbe 1 to 5 mm, or 1 to 4 mm, where the height of the upper and lowerportions can be 1 to 2 mm and the height of a middle portion can be 0.3to 2, 0.4 to 1, or 0.5 to 0.8 mm.

FIGS. 4a-i represent a sequential series of schematic showing an exampleof herein using a mold and a window as disclosed in FIG. 2. A mold 208is provided having at least two recess 211 (one is shown). The tworecesses are located at a select distance, ds, (not shown) from eachother. The location of the recesses can correspond to the location ofendpoint detection sensors elements in a chemical mechanical polishingtool. The recess dimension 210 and the lower portion 204 l of the window204 are selected such that the lower portion 204 l of the window 204fits, preferably fits precisely and snuggly without any or anysignificant gaps between sides of the window 204 and the sides of therecess 211. As shown, the depth 209 of the recess 211 can be the same orsubstantially the same as the height, hi, of the lower portion 204 l ofthe window 204. If a window 304 as shown in FIG. 3 is used, the recesscan mate with either the lower portion 304 l or with both the lowerportion 304 l, and the middle portion 304 m. If a plug type window 04 asis shown in FIG. 1b is used, the depth 209 is less than the full heightof the window 04. In each instance, an upper portion of the window (e.g.204 u or 304 u, latter not shown) protrudes above a surface 212 of themold 208. The mold can be made from any material, for example, a metalsuch as steel. The mold can also be fitted with a removable collararound its outer perimeter that can shape the outer perimeter of thelayer 205. The mold includes a top surface 212. As shown in FIG. 4c , apolishing material 205 is applied over the top surface 212 and,optionally, over the upper portion (e.g., 204 u as shown) of the window(e.g. 204 as shown). The polishing material can be applied by coating(e.g., spray coating), casting, molding (e.g. injection molding),additive manufacture (e.g. 3D printing), or laminating. The polishinglayer material 205 can be applied in polymerized form or can be appliedas a pre-polymer composition and polymerized or can be applied in acurable form and cured while in the mold 208. The polishing layer 205 asinitially formed can have thickness 215 equal to, substantially equalto, or greater than the height of the upper portion of the window 204that is extending above the surface 212. In FIG. 4c , the polishinglayer 205 as initially formed has a thickness greater than the height ofthe upper portion of the window 204. In this instance, the polishinglayer material 205 can cover the top surface of the window 204 by anexcess amount 213 and the top surface of the window 204 can be exposedby a reveal step to arrive at the structure in FIG. 4d . In otherinstances—e.g., where injection molding is used where a top portion of amold contacts a top surface of the window, coating with a mask over thewindow 204, or additive printing are used—the polishing material 205 maynot be on the top surface of the window 204 such that the applying stepdirectly forms the structure of FIG. 4d . When a reveal step is usedthis step can also provide desired texture or controlled surfaceroughness to the top surface of the polishing layer 205. The structurecan be such that the windows do not protrude above the top surface ofthe polishing layer 205. The top surface of the windows can be coplanarwith the top surface 205 t of the polishing layer 205.

After forming the polishing layer 205 (before or after any needed revealstep), the polishing layer with at least two windows in two aperturesformed in the preceding steps is removed from the mold 208 exposing aninterface surface 205 i and the lower portion of the windows 204. (SeeFIG. 4e showing the polishing layer and window removed from mold 208 andinverted). Note, that while FIG. 4 shows the method using a window witha structure as in FIG. 2 with a smaller upper portion and a larger lowerportion, the method is equally applicable to a window that has a simpleplug shape or to a window that has three portions as shown in FIG. 3.Note further that while FIG. 4 shows that the entire larger lowerportion fits in the recess, it is also contemplated that a portion ofthe larger lower portion could extend above the top surface 212 of themold. Similarly, if a window with three portions is used, the mold couldhave a recess for only the lowest portion 304 l (or a portion there) ora stepped recess to accept both the lowest portion 304 l and at least aportion of the middle portion 304 m.

Alternatively, the structure as shown in FIG. 4e , can be made byforming two or more apertures in a pre-formed polishing layer theapertures being formed at a select distance, ds, from each other. Thelocation of the apertures can correspond to the positioning of endpointdetection sensors in a chemical mechanical polishing tool. A window canthen be inserted into each aperture such that a portion of the windowextends above the interface surface 205 i of the polishing layer. Inthis instance, an adhesive can be applied to at least a portion of theregions of the polishing layer contacting the window and at least aportion of the regions of the window contacting the polishing layer.Particularly, the adhesive can be applied at rim portions 204 r and 304ur (as shown in FIG. 2 and FIG. 3, respectively) of the window and theadjacent polishing layer.

As shown in FIG. 4f , the polishing layer with windows can then havesubpad 206 formed on the interface surface 205 i and the lower portion204 u. During this process the polishing layer 205 with windows can besupported on a support 218 (not shown). The support could be a mold.This support mold could also be fitted with a removable collar aroundits outer perimeter, which support can be used to define the outerperimeter and the thickness of the subpad material 206. The subpadmaterial can be applied in already polymerized form or can bepolymerized or cured after application to the interface 205 i and thewindows. While the subpad material 206 is shown with a planar topsurface and extending above the window at an excess thickness amount213, the top surface can alternatively generally follow the contour ofthe interface surface 205 i and the window portion extending from thatsurface such that there is a raised portion of subpad material where thewindow is found. This raised portion can be used to identify where toapply the reveal step to form a structure as shown in FIG. 4h with arecess area 214.

As shown in FIG. 4g , the excess subpad material 206 can be removed toreveal the window 204, by machining, grinding or etching. As shown inFIGS. 4h and 4i , (FIG. 4i is FIG. 4h inverted) the window material canbe further etched back to provide a recess area 214. Alternatively, if araised portion of subpad 206 is used to identify the location of thewindow, a selective etch or well machining can be done in that locationto reveal the window and form the recess.

FIG. 5 shows use of a window 504 similar to that in FIG. 3 with adhesive520 applied in certain portions (for example, the adhesive can beapplied on at least one rim or flange) to hold the window in thepolishing layer 505. The extended middle portion of the window 504serves as a flange that further can hold the window in its desiredlocation.

This disclosure further encompasses the following aspects.

Aspect 1: A method of manufacturing a chemical mechanical polishing padhaving two or more end point detection windows comprising providing astructure that includes a polishing layer having a top surface defininga horizontal direction, a bottom surface, and two or more aperturesextending from the top surface to the bottom surface wherein each of thetwo or more apertures has a transparent window located in the aperture,where each of the windows has a portion extending outward from thebottom surface of the polishing layer, wherein the two or more aperturesare located at select distance from each other, applying a subpadmaterial on the bottom surface and the portion of the windows extendingoutward from the bottom surface, and revealing the windows by removing aportion of the subpad material.

Aspect 2. The method of Aspect 1 wherein the providing of the structurecomprises providing a mold with a surface and two or more recesses inthe surface each recess formed to receive a portion of one of thewindows, the recesses being located at the select distance from eachother, inserting the windows into the recesses such that a top portionof each the windows extends above the mold surface, forming thepolishing layer on the mold surface and around a periphery of the topportion of the windows, and removing the polishing layer with thewindows from the mold.

Aspect 3. The method of Aspect 2 wherein in forming the polishing layera top surface of the windows is covered by a portion of the polishinglayer and further comprising revealing the top surface of the windows byremoval of a portion of the polishing layer.

Aspect 4. The method of Aspect 1 wherein the providing of the structurecomprises forming the two or more apertures in the polishing layer atthe select distance from each other, providing the windows for eachaperture, each window having a top portion and a flange portion, whereinthe top portion has an area in the horizontal direction that is smallerthan an area of the flange portion in the horizontal direction such thatthe second portion forms a rim, applying adhesive to the bottom surfaceof the polishing layer adjacent the aperture, to the rim of the windows,or both, and inserting into each of the two or more the apertures one ofthe windows such that the polishing layer surrounds a periphery of thetop portion of each of the windows in the horizontal direction.

Aspect 5. The method of Aspect 4 wherein at least a segment the flangeportion of the windows forms the portion of the window that extends fromthe bottom surface of the polishing layer.

Aspect 6. The method of Aspect 4 wherein the flange portion of thewindows is between the top portion of the windows and a bottom portionof the windows, wherein the bottom portion has an area in the horizontaldirection that is smaller than the area of the flange portion in thehorizontal direction, wherein the bottom portion, or the bottom portionand at least a segment of the flange portion form the portion of thewindows extending outward from the bottom surface of the polishing layerand the area of the flange portion in the horizontal direction is largerthan the area of the portion of the window extending outward from thebottom surface of the polishing layer.

Aspect 7. The method of any one of Aspects 1-6 wherein the subpadmaterial is applied by coating, injection molding, printing.

Aspect 8. The method of any one of Aspects 1-7 wherein an amount of theportion of the window extending outward from the bottom surface of thepolishing layer is removed during or after the removing of a portion ofthe subpad material to form a recessed window.

Aspect 9. The method of any one of Aspects 1-8 wherein there are threeor more apertures and windows and the select distance between adjacentapertures is the same or different.

Aspect 10. The method of any one of Aspects 1-9 wherein the selectdistance corresponds to a distance of placement of endpoint detectors ina chemical mechanical polishing apparatus having two or more endpointdetectors.

Aspect 11: The method of any one of Aspects 1-10 wherein each of theapertures in the polishing layer and each of the windows in the pad areat a distance from a center of the polishing layer, preferably a radialdistance, which is the same for each aperture and equidistant from thecenter.

Aspect 12: The method of any one of Aspects 1-11 wherein there are threewindows that are equidistant from each other.

Aspect 13: The method of any one of Aspects 1-12 wherein the windows areof the same size.

All ranges disclosed herein are inclusive of the endpoints, and theendpoints are independently combinable with each other (e.g., ranges of“up to 25 wt. %, or, more specifically, 5 wt. % to 20 wt. %”, isinclusive of the endpoints and all intermediate values of the ranges of“5 wt. % to 25 wt. %,” etc.). Moreover, stated upper and lower limitscan be combined to form ranges (e.g. “at least 1 or at least 2 weightpercent” and “up to 10 or 5 weight percent” can be combined as theranges “1 to 10 weight percent”, or “1 to 5 weight percent” or “2 to 10weight percent” or “2 to 5 weight percent”).

The disclosure may alternately comprise, consist of, or consistessentially of, any appropriate components herein disclosed. Thedisclosure may additionally, or alternatively, be formulated so as to bedevoid, or substantially free, of any components, materials,ingredients, adjuvants or species used in the prior art compositions orthat are otherwise not necessary to the achievement of the function orobjectives of the present disclosure.

All cited patents, patent applications, and other references areincorporated herein by reference in their entirety. However, if a termin the present application contradicts or conflicts with a term in theincorporated reference, the term from the present application takesprecedence over the conflicting term from the incorporated reference.

Unless specified to the contrary herein, all test standards are the mostrecent standard in effect as of the filing date of this application, or,if priority is claimed, the filing date of the earliest priorityapplication in which the test standard appears.

References numerals stand for the element/component as listed below:

-   01, 201 polishing pad-   03, 205 t top surface of polishing pad-   04, 204, 304, 504 windows-   05, 205, 505 polishing layer-   06, 206, 506 subpad-   204 u, 304 u upper portion of window, generally surrounded in its    periphery by polishing-   player-   204 l, 304 l lower portion of window, generally at least part of its    height is surrounded in its-   periphery by subpad material. 204 l can be flange-   304 m middle portion of window or flange-   208 mold-   209 depth of recess in mold-   210 horizontal dimension of recess in mold-   211 recess in mold-   212 top surface of mold-   205 i interface surface of polishing layer upon which subpad is    formed-   213 excess height of subpad material applied over window-   214 recess formed on bottom side (subpad side) of window-   215 excess height of polishing layer material applied over window-   520 adhesive

What is claimed is:
 1. A method of manufacturing a chemical mechanicalpolishing pad having two or more end point detection windows comprising:providing a structure that includes a polishing layer having a topsurface defining a horizontal direction, a bottom surface, and two ormore apertures extending from the top surface to the bottom surfacewherein each of the two or more apertures has a transparent windowlocated in the aperture, wherein each of the windows has a portionextending outward from the bottom surface of the polishing layer,wherein the two or more apertures are located at select distance fromeach other, applying a subpad material on the bottom surface and theportion of the windows extending outward from the bottom surface of thepolishing layer and wherein the two or more apertures remain at theselect distance from each other, revealing the windows by removing aportion of the subpad material.
 2. The method of claim 1 wherein theproviding of the structure includes the following: providing a mold witha surface and two or more recesses in the surface each recess formed toreceive a portion of one of the windows, the recesses being located atthe select distance from each other, inserting the windows into therecesses such that a top portion of each the windows extends above themold surface, forming the polishing layer on the mold surface and arounda periphery of the top portion of the windows, and removing thepolishing layer with the windows from the mold.
 3. The method of claim 2wherein in forming the polishing layer a top surface of the windows iscovered by a portion of the polishing layer and further comprisingrevealing the top surface of the windows by removal of a portion of thepolishing layer.
 4. The method of claim 1 wherein the providing of thestructure comprises forming the two or more apertures in the polishinglayer at the select distance from each other, providing the windows foreach aperture, each window having a top portion and a flange portion,wherein the top portion has an area in the horizontal direction that issmaller than an area of the flange portion in the horizontal directionsuch that the second portion forms a rim, applying adhesive to thebottom surface of the polishing layer adjacent the aperture, to the rimof the windows, or both, and inserting into each of the two or more theapertures one of the windows such that the polishing layer surrounds aperiphery of the top portion of each of the windows in the horizontaldirection.
 5. The method of claim 4 wherein at least a segment theflange portion of the windows forms the portion of the window thatextends from the bottom surface of the polishing layer.
 6. The method ofclaim 4 wherein the flange portion of the windows is between the topportion of the windows and a bottom portion of the windows, wherein thebottom portion has an area in the horizontal direction that is smallerthan the area of the flange portion in the horizontal direction, whereinthe bottom portion, or the bottom portion and at least a segment of theflange portion form the portion of the windows extending outward fromthe bottom surface of the polishing layer and the area of the flangeportion in the horizontal direction is larger than the area of theportion of the window extending outward from the bottom surface of thepolishing layer.
 7. The method of claim 1 wherein the subpad material isapplied by coating, injection molding, or printing.
 8. The method ofclaim 1 wherein an amount of the portion of the window extending outwardfrom the bottom surface of the polishing layer is removed during orafter the removing of a portion of the subpad material to form arecessed window.
 9. The method of claim 1 wherein there are three ormore apertures and windows and the select distance between adjacentapertures is the same or different.
 10. The method of claim 1 whereinthe select distance corresponds to a distance of placement of endpointdetectors in a chemical mechanical polishing apparatus having two ormore endpoint detectors.